A girl on Instagram DM me about my boyfriend...

So me and this guy met and dated in September, he was the nicest guy ever, honestly the nicest guy I’ve ever met. We ended because of me, I wasn’t over my ex completely and wanted time to heal alone. We started talking again Saturday and hung out on Monday.

And im SO confused. This doesn’t sound like him at all. He’s never been aggressive with me ever. He’s never talked to me even close to being disrespectfully. I haven’t asked him about it and I don’t even know what to say. I’m thinking of saying no next time we’re hanging out to having sex? And see how he reacts? But I honestly don’t see him being like that towards me.... what do I do